Protein interactions, actin filaments. Animation showing actin filaments across bottom within a cell, surrounded by proteins in the cytoplasm. The proteins include those, such as calmodulin see K003/3837, that bind to other proteins to activate the myosin and actin filaments, causing them to contract. Actin and myosin filaments form part of the cell磗 cytoskeleton, allowing it to contract and move cytokinesis. This clip is part of a sequence showing cellular protein interactions. For the entire sequence, see clips K003/3837 to K003/3831.